Try replacing the front and rear motor mounts. I'd say there is a 66% chance that what you think is the clutch chattering is actually the motor moving around more now that you've changed the engagement cycle by replacing the clutch.
Buying used items is hit or miss - but it is almost never a good idea to buy used “consumable” items (filters of any kind, brake pads, clutch, etc.). Paint is a consumable item. If you ever start to get suckered into buying used consumables because of price or something - just remind yourself how silly it would be to buy used paint.